Speech Signal Analysis in Phase Domain

Speech signal analysis based on the Phase Spectrum (PS) in the recent years becomes more popular to the researchers due to its attractive properties. Though some problem arises during its processing but appropriate modification gives the useful result. In this study, we proposed a new method of speech signal analysis based on its phase spectral representation. After analyzing the PS we modified it vocal tract dominated spectrum by utilizing the minimum-phase stable component of the speech spectrum. The modified signal holding only the phase spectral component is used for the parametric modeling of the speech signal to estimate the characteristics of vocal tract perfectly. This extracted feature was found to provide complementary evidence from the magnitude spectrum of speech but with better resolution. According to perceptual analysis, the PS takes precedence over the magnitude spectrum. This research utilizes the Group Delay (GD) spectrum as a representative of the PS because of its meaningful characteristic. All pole modeling is performed on the signal evaluated from the GD spectrum to find the resonances of the vocal tract system accurately. The effectiveness of the method is tested by synthesizing some vowels over a range of pitch periods from low to high pitched speech. The validity of the proposed method is also verified by plotting the formant contour on the spectrogram of a sentence from the TIMIT database and standard F2-F1 plot of natural speech spoken by male and female speakers. The proposed method performs better than the state-of-the-art methods.